Thanks for the report. This was something I filed and saw a while back as https://mcneel.myjetbrains.com/youtrack/issue/RH-38255 but it since has not been seen. Are you seeing this issue in all files or just one? My suspicion is that there’s still a series of steps to reproduce it that I’m missing. If you stumble upon any, please let me know. The issue when I filed it was due to any amount of reflection roughness being added to a metal.